U.S. patent application number 13/427355 was filed with the patent office on 2012-08-09 for crosslinkable fluororubber composition and crosslinked rubber article.
This patent application is currently assigned to Asahi Glass Company, Limited. Invention is credited to Tomoyuki Fujita, Makoto HONDA, Daisuke Shirakawa, Kunio Watanabe.
Application Number | 20120202950 13/427355 |
Document ID | / |
Family ID | 43826382 |
Filed Date | 2012-08-09 |
United States Patent
Application |
20120202950 |
Kind Code |
A1 |
HONDA; Makoto ; et
al. |
August 9, 2012 |
CROSSLINKABLE FLUORORUBBER COMPOSITION AND CROSSLINKED RUBBER
ARTICLE
Abstract
Obtaining a crosslinked rubber with high flexibility at low
temperature includes crosslinking a fluororubber composition. The
fluororubber composition includes a fluororubber and a compound of
formula (X--).sub.x(Z--).sub.zY. In the formula, X is
U--(CF.sub.2).sub.aO(CF.sub.2CF.sub.2O).sub.b--; Z is
R.sup.FO(CF.sub.2CF.sub.2O).sub.c--; Y is a (x+z) valent perfluoro
saturated hydrocarbon group, optionally interrupted by an etheric
oxygen atom; x is an integer of at least 3; z is an integer of at
least 0; U is a monovalent group with an unsaturated hydrocarbon, a
bromine atom, an iodine atom, or a combination thereof; R.sup.F is
a C.sub.1-20 linear perfluoroalkyl group, optionally interrupted by
an etheric oxygen atom; a is an integer of from 0 to 20; b is an
integer of from 1 to 200; and c is an integer of from 3 to 200.
Inventors: |
HONDA; Makoto; (Tokyo,
JP) ; Fujita; Tomoyuki; (Tokyo, JP) ;
Watanabe; Kunio; (Tokyo, JP) ; Shirakawa;
Daisuke; (Tokyo, JP) |
Assignee: |
Asahi Glass Company,
Limited
Tokyo
JP
|
Family ID: |
43826382 |
Appl. No.: |
13/427355 |
Filed: |
March 22, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/JP2010/067161 |
Sep 30, 2010 |
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13427355 |
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Current U.S.
Class: |
525/276 |
Current CPC
Class: |
C08L 71/02 20130101;
C08G 2650/46 20130101; C08K 5/20 20130101; C08L 27/12 20130101;
C08G 65/007 20130101; C08K 5/0025 20130101; C08L 27/12 20130101;
C08L 71/00 20130101; C08L 71/00 20130101; C08G 2650/48 20130101;
C08K 5/20 20130101; C08K 5/14 20130101; C08L 27/12 20130101; C08L
2666/22 20130101; C08L 27/12 20130101 |
Class at
Publication: |
525/276 |
International
Class: |
C08L 27/18 20060101
C08L027/18 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 1, 2009 |
JP |
2009-229424 |
Claims
1. A crosslinkable fluororubber composition comprising a
fluororubber and a compound represented by the following formula
(A): (X--).sub.x(Z--).sub.zY (A) wherein X is a group represented
by the following formula (X), Z is a group represented by the
following formula (Z), Y is a (x+z) valent perfluoro saturated
hydrocarbon group or such a group having an etheric oxygen atom
inserted between carbon atoms thereof, x is an integer of at least
3, z is an integer of at least 0, x+z is an integer of at least 3,
U--(CF.sub.2).sub.aO(CF.sub.2CF.sub.2O).sub.b-- (X)
R.sup.FO(CF.sub.2CF.sub.2O).sub.c-- (Z) wherein U is a monovalent
group having at least one member selected from the group consisting
of an unsaturated hydrocarbon, a bromine atom and an iodine atom,
R.sup.F is a C.sub.1-20 linear perfluoroalkyl group or such a group
having an etheric oxygen atom inserted between carbon atoms
thereof, a is an integer of from 0 to 20, b is an integer of from 1
to 200, and c is an integer of from 3 to 200.
2. The crosslinkable fluororubber composition according to claim 1,
wherein the compound represented by the formula (A) is a compound
represented by the following formula (A1): (X--).sub.x1Y (A1)
wherein x1 is an integer of 3 or 4.
3. The crosslinkable fluororubber composition according to claim 2,
wherein x1 in the formula (A1) is 3, and Y is any one of the groups
(Y.sup.3-1) to (Y.sup.3-4) represented by the following formulae:
##STR00011##
4. The crosslinkable fluororubber composition according to claim 1,
wherein the compound represented by the formula (A) is a compound
represented by the following formula (A2): ##STR00012## wherein
each of b1, b2 and b3 which are independent of one another, is an
integer of from 1 to 20.
5. The crosslinkable fluororubber composition according to claim 1,
wherein the compound represented by the formula (A) has a number
average molecular weight (Mn) of from 500 to 100,000.
6. The crosslinkable fluororubber composition according to claim 1,
wherein the compound represented by the formula (A) has a ratio
(Mw/Mn) of the mass average molecular weight (Mw) to the number
average molecular weight (Mn) of from 1.0 to 2.0.
7. The crosslinkable fluororubber composition according to claim 1,
which contains the compound represented by the formula (A) in an
amount of from 1 to 50 parts by mass per 100 parts by mass of the
fluororubber.
8. The crosslinkable fluororubber composition according to claim 1,
wherein the fluororubber is at least one member selected from the
group consisting of a tetrafluoroethylene/propylene copolymer, a
vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene
copolymer and a tetrafluoroethylene/perfluoroalkyl vinyl ether
copolymer.
9. The crosslinkable fluororubber composition according to claim 1,
which further contains an organic peroxide.
10. A crosslinked rubber article formed by crosslinking the
crosslinkable fluororubber composition as defined in claim 1.
11. The crosslinked rubber article according to claim 10, which is
a sealing material.
Description
TECHNICAL FIELD
[0001] The present invention relates to a crosslinkable
fluororubber composition which can give a crosslinked rubber
article excellent in flexibility at a low temperature, and the
crosslinked rubber article obtained therefrom.
BACKGROUND ART
[0002] As crosslinking treatment of a fluororubber, a method of
peroxide-crosslinking a fluororubber by mixing it with an organic
peroxide and heating the mixture, or a method of
radiation-crosslinking a fluororubber by irradiating it with
radioactive rays, as disclosed in the following Patent Document 1,
have been known. At that time, in order to improve the crosslinking
property of a fluororubber or the properties of a crosslinked
rubber article obtainable, heretofore, a polyfunctional compound
has been blended as a crosslinking coagent.
[0003] As the polyfunctional compound, triallyl isocyanurate has
been preferably used (See Non-Patent Document 1 and Patent Document
1). By using triallyl isocyanurate as a crosslinking coagent, it is
possible to improve a crosslinking rate of a fluororubber. Further,
a triazine ring structure excellent in the heat resistance is
inserted into a crosslinking site of a fluororubber, and therefore
it is advantageous in that a crosslinked rubber article excellent
in the heat resistance or mechanical properties is obtainable.
PRIOR ART DOCUMENT
Non-Patent Document
[0004] Non-Patent Document 1: Handbook of Fluororesins, pages 616
to 622 and 577 to 578, edited by Satokawa (published in 1990 by THE
NIKKAN KOGYO SHIMBUN, LTD.)
Patent Document
[0004] [0005] Patent Document 1: JP-A-7-179705
DISCLOSURE OF INVENTION
Technical Problem
[0006] However, a fluororubber, especially a fluororubber having a
tetrafluoroethylene as a copolymer component is poor in flexibility
at a low temperature, and thus had a problem in sealing property
under a low temperature environment.
[0007] Accordingly, it is an object of the present invention to
provide a crosslinkable fluororubber composition which can give a
crosslinked rubber article excellent in flexibility at a low
temperature, and the crosslinked rubber article.
Solution to Problem
[0008] The present invention provides the following:
[1] A crosslinkable fluororubber composition comprising a
fluororubber and a compound represented by the following formula
(A):
(X--).sub.x(Z--).sub.zY (A)
wherein X is a group represented by the following formula (X), Z is
a group represented by the following formula (Z), Y is a (x+z)
valent perfluoro saturated hydrocarbon group or such a group having
an etheric oxygen atom inserted between carbon atoms thereof, x is
an integer of at least 3, z is an integer of at least 0, x+z is an
integer of at least 3,
U--(CF.sub.2).sub.aO(CF.sub.2CF.sub.2O).sub.b-- (X)
R.sup.FO(CF.sub.2CF.sub.2O).sub.c-- (Z)
wherein U is a monovalent group having at least one member selected
from the group consisting of an unsaturated hydrocarbon, a bromine
atom and an iodine atom, R.sup.F is a C.sub.1-20 linear
perfluoroalkyl group or such a group having an etheric oxygen atom
inserted between carbon atoms thereof, a is an integer of from 0 to
20, b is an integer of from 1 to 200, and c is an integer of from 3
to 200. [2] The crosslinkable fluororubber composition according to
[1], wherein the compound represented by the formula (A) is a
compound represented by the following formula (A1):
(X--).sub.x1Y (A1)
wherein x1 is an integer of 3 or 4. [3] The crosslinkable
fluororubber composition according to [2], wherein x1 in the
formula (A1) is 3, and Y is any one of the groups (Y.sup.3-1) to
(Y.sup.3-4) represented by the following formulae:
##STR00001##
[4] The crosslinkable fluororubber composition according to [1],
wherein the compound represented by the formula (A) is a compound
represented by the following formula (A2):
##STR00002##
wherein each of b1, b2 and b3 which are independent of one another,
is an integer of from 1 to 20. [5] The crosslinkable fluororubber
composition according to any one of [1] to [4], wherein the
compound represented by the formula (A) has a number average
molecular weight (Mn) of from 500 to 100,000. [6] The crosslinkable
fluororubber composition according to any one of [1] to [5],
wherein the compound represented by the formula (A) has a ratio
(Mw/Mn) of the mass average molecular weight (Mw) to the number
average molecular weight (Mn) of from 1.0 to 2.0. [7] The
crosslinkable fluororubber composition according to any one of [1]
to [6], which contains the compound represented by the formula (A)
in an amount of from 1 to 50 parts by mass per 100 parts by mass of
the fluororubber. [8] The crosslinkable fluororubber composition
according to any one of [1] to [7], wherein the fluororubber is at
least one member selected from the group consisting of a
tetrafluoroethylene/propylene copolymer, a vinylidene
fluoride/tetrafluoroethylene/hexafluoropropylene copolymer and a
tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer. [9] The
crosslinkable fluororubber composition according to any one of [1]
to [8], which further contains an organic peroxide. [10] A
crosslinked rubber article formed by crosslinking the crosslinkable
fluororubber composition as defined in any one of [1] to [9]. [11]
The crosslinked rubber article according to [10], which is a
sealing material.
Advantageous Effects of Invention
[0009] The crosslinkable fluororubber composition of the present
invention, containing the compound represented by the above formula
(A), has an excellent crosslinkability such as peroxide
crosslinkability or radiation crosslinkability and a high
crosslinking rate. Further, the crosslinked rubber article of the
present invention, formed by crosslinking the crosslinkable
fluororubber composition, has excellent flexibility at a low
temperature and good low-temperature characteristics, and also has
excellent basic properties such as strength, hardness, modulus and
compression set.
DESCRIPTION OF EMBODIMENTS
[0010] Hereinafter in this specification, a compound represented by
the formula (A) will be also referred to as a compound (A). The
same applies to other compounds. Further, a group represented by
the formula (X) will be also referred to as a group (X). The same
applies to other groups.
(Crosslinkable Fluororubber Composition)
[0011] The crosslinkable fluororubber composition of the present
invention has a composition comprising at least a fluororubber and
the following compound (A):
(X--).sub.x(Z--).sub.ZY (A)
[Compound (A)]
[0012] Now, the compound (A) to be used for the crosslinkable
fluororubber composition of the present invention will be
described. The compound (A) functions as a crosslinking coagent in
the crosslinkable fluororubber composition of the present
invention.
[0013] X in the compound (A) is a monovalent group represented by
the following formula (X):
U--(CF.sub.2).sub.aO(CF.sub.2CF.sub.2O).sub.b-- (X)
[0014] In the group (X), a is an integer of from 0 to 20,
preferably an integer of from 0 to 10, particularly preferably an
integer of from 0 to 2. Further, b is an integer of from 1 to 200,
preferably an integer of from 1 to 100, particularly preferably an
integer of from 1 to 20. Further, U is a monovalent group having at
least one member selected from the group consisting of an
unsaturated hydrocarbon, a bromine atom and an iodine atom. As
specific examples of a case where U is the group having an
unsaturated hydrocarbon, the following structures (U-1) to (U-13)
may be mentioned.
##STR00003##
[0015] Among them, (U-8), (U-9), (U-11) or (U-12) is preferred
since it has a structure having an allyl group bonded to N, and
(U-11) or (U-12) is particularly preferred.
[0016] Further, as specific examples of a case where U is the
monovalent group having a bromine atom, the following structures
may be mentioned. In the formulae, n is an integer of from 1 to
3.
Br(CH.sub.2).sub.n--
Br(CH.sub.2).sub.nC(O)O--CH.sub.2
[0017] Further, as specific examples of a case where U is the
monovalent group having an iodine atom, the following structures
may be mentioned. In the formulae, n is an integer of from 1 to
3.
I(CH.sub.2).sub.n--
I(CH.sub.2).sub.nC(O)O--CH.sub.2
[0018] As the group (X), a structure represented by the following
formula (X1) is preferred.
U--CF.sub.2O(CF.sub.2CF.sub.2O).sub.b-- (X1)
[0019] In the compound (A), Z is a monovalent group represented by
the following formula (Z):
R.sup.FO(CF.sub.2CF.sub.2O).sub.c-- (Z)
[0020] In the group (Z), c is an integer of from 3 to 200,
preferably an integer of from 3 to 100, particularly preferably an
integer of from 5 to 50. Further, R.sup.F is a C.sub.1-20 linear
perfluoroalkyl group or such a group having an etheric oxygen atom
inserted between carbon atoms thereof, and it particularly
preferably has from 1 to 16 carbon atoms. As specific examples of
R.sup.F, the following groups may be mentioned. In the formulae, is
an integer of from 0 to 15, C.sub.Y.sup.F is a perfluorocyclohexyl
group, t is an integer of from 0 to 15, A.sub.d.sup.F is a
perfluoroadamantyl group, and t is an integer of from 0 to 15.
CF.sub.3(CF.sub.2).sub.s--
C.sub.y.sup.F--(CF.sub.2).sub.t--
A.sub.d.sup.F--(CF.sub.2).sub.t--
[0021] In the compound (A), Y is a (x+z) valent perfluoro saturated
hydrocarbon group or such a group having an etheric oxygen atom
inserted between carbon atoms thereof, x+z as a valence of the
group (Y) is an integer of at least 3, preferably from 3 to 110,
particularly preferably from 3 to 9.
[0022] As specific examples of a case where the group (Y) is a
trivalent group, the groups (Y.sup.3-1) to (Y.sup.3-4) may be
mentioned, wherein the group (Y.sup.3-4) is a
perfluorocyclohexane-1,3,5-triyl group. Further, as specific
examples of a case where the group (Y) is a tetravalent group, the
groups (Y.sup.4-1) to (Y.sup.4-5) may be mentioned. Further, as a
specific example of a case where the group (Y) is a pentavalent
group, the group (Y.sup.5-1) may be mentioned.
##STR00004## ##STR00005## (Y.sup.5-1)
[0023] As the group (Y), the groups (Y.sup.3-1) to (Y.sup.3-4) are
preferred.
[0024] The compound (A) is a compound in which x number of groups
(X) and z number of groups (Z) are bonded to the group (Y), wherein
x is an integer of at least 3, z is an integer of at least 0, and
(x+z) is an integer of at least 3. That is, the compound (A) is a
compound in which at least three groups (X) are bonded to the group
(Y) and the group (Z) is optionally bonded thereto.
[0025] Since the compound (A) has at least three groups (X) having
a linear perfluoropolyether bond (a moiety of
"--(CF.sub.2CF.sub.2O).sub.b--" in the group (X)), the compound (A)
is excellent in flexibility at a low temperature. Further, the
group (X) has U (hereinafter, referred to as a reactive group (U))
as a monovalent group having at least one member selected from the
group consisting of an unsaturated hydrocarbon, a bromine atom and
an iodine atom. Therefore, at the time of crosslinking treatment of
a fluororubber composition containing the compound (A), the
compound (A) is bonded to a fluororubber and further
three-dimensionally crosslinked therewith, whereby the compound (A)
is stably incorporated into the fluororubber. Accordingly, it is
possible to suppress bleeding out of the compound (A) on the
surface of a crosslinked fluororubber as a final product, and it is
possible to maintain excellent low-temperature characteristics over
a long period. Further, since it is thus possible to suppress
bleeding out of the compound (A), it is possible to suppress mold
contamination at the time of molding, stickiness of the surface,
etc. Further, the compound (A) is bonded to a fluororubber and
further three-dimensionally crosslinked therewith, whereby it is
possible to improve basic properties such as strength, hardness,
modulus or compression set of a crosslinked rubber article
obtainable.
[0026] In the compound (A), x is an integer of at least 3,
preferably from 3 to 100, particularly preferably from 3 to 8.
Further, z is an integer of at least 0, preferably from 0 to 10,
more preferably from 0 to 1, particularly preferably 0. Further,
(x+z) is an integer of at least 3, preferably from 3 to 110, more
preferably from 3 to 9, particularly preferably 3 or 4. When x is
at least 3, the compound (A) can be three-dimensional crosslinked
in the fluororubber.
[0027] That is, the compound (A) is preferably a compound
represented by the following formula (A1):
(X--).sub.x1Y (A1)
wherein x1 is an integer of 3 or 4.
[0028] As specific examples of a case where the group (Y) is a
trivalent group in the compound (A), the compounds (A.sup.3-1) to
(A.sup.3-4) may be mentioned. Further, as specific examples of a
case where the group (Y) is a tetravalent group, the compounds
(A.sup.4-1) to (A.sup.4-10) may be mentioned. Among them, from the
viewpoint of balance between crosslinkability and low-temperature
characteristics, (A.sup.3-1), (A.sup.4-1) or (A.sup.4-2) is
preferred.
##STR00006## ##STR00007##
[0029] A preferred specific example of the compound (A) may be a
compound represented by the following formula (A2):
##STR00008##
wherein each of b1, b2 and b3 which are independent of one another,
is an integer of from 1 to 20, preferably an integer of from 1 to
10.
[0030] The number average molecular weight (hereinafter also
referred to as Mn) of the compound (A) is preferably from 500 to
100,000, more preferably from 1,000 to 20,000. If Mn is less than
500, the low-temperature characteristics tend to be insufficient,
and if Mn exceeds 100,000, the crosslinkability tends to
deteriorate.
[0031] The ratio (hereinafter, also referred to as Mw/Mn) of the
mass average molecular weight (hereinafter, also referred to as Mw)
to the number average molecular weight (Mn) of the compound (A) is
preferably from 1.0 to 2.0.
[0032] Further, in the present invention, Mn and Mw are values
measured by gel permeation chromatography (hereinafter, referred to
as GPC), and Mw/Mn is a value determined from Mn and Mw measured by
GPC.
[0033] The compound (A) may, for example, be produced in such a
manner that the compound (AO) is produced by a method disclosed in
WO2005/068534, and the terminal of the compound is converted by a
known method. In the compound (AO), Rd is a lower alkyl group.
(R.sup.dOC(O)--CF.sub.2O(CF.sub.2CF.sub.2O).sub.b--).sub.a--).sub.zY
(AO)
[0034] Further, the value of x or z may be changed depending upon
the reaction conditions of the fluorination step in the production
of (AO) (e.g. [0043] and [0044] in JP-A-2009-197210). Accordingly,
there is a case where the compound (A) contains a compound wherein
x is at most 2. In such a case, the compound wherein x is at most
2, is not included in the compound (A) of the present invention,
but at the time of using the compound (A) as a crosslinking coagent
of a fluororubber, the compound (A) may be used as it is, without
separating the compound wherein x at most 2.
[0035] Further, in this specification, since the compound (A) has
at least x number of the reactive groups (U), the compound (A) will
be sometimes referred to as an x functional compound. The compound
(A) will be referred to as e.g. a trifunctional compound when x is
3, or a tetrafunctional compound when x is 4. Further, the compound
wherein x is at most 2, as a by-product, will be also referred to
as a monofunctional compound or a bifunctional compound.
[0036] The compound (A) obtained by the reaction may be used as it
is as a solution after the reaction, or it may be used after
removing an unnecessary solvent and raw materials by e.g.
concentration. Further, purification may be carried out as the case
requires. As a means for the purification, washing with water or an
organic solvent which undergoes phase separation from the compound
(A), removal of e.g. metal impurities or anion impurities by an ion
adsorbing polymer, supercritical extraction or column
chromatography may be mentioned, and these means may be
combined.
[0037] In the crosslinkable fluororubber composition of the present
invention, the content of the compound (A) is preferably from 1 to
50 parts by mass, more preferably from 5 to 50 parts by mass, most
preferably from 10 to 50 parts by mass, based on 100 parts by mass
of the fluororubber. If the content of the compound (A) is too low,
the flexibility at a low temperature cannot be improved in some
cases, and therefore the effect of improving the low-temperature
characteristics tend to be small. If the content of the compound
(A) is too high, the compound (A) tends to bleed out from a rubber
article after crosslinking. If the content of the compound (A) is
from 1 to 50 parts by mass based on 100 parts by mass of the
fluororubber, the crosslinking rate becomes high, and a crosslinked
rubber article excellent in low-temperature characteristics can
readily be obtained.
[Fluororubber]
[0038] Now, a fluororubber to be used for the crosslinkable
fluororubber composition of the present invention will be
described.
[0039] The fluororubber is not particularly limited. A vinylidene
fluoride/hexafluoropropylene copolymer, a vinylidene
fluoride/tetrafluoroethylene/hexafluoropropylene copolymer, a
vinylidene fluoride/chlorotrifluoroethylene copolymer, a
tetrafluoroethylene/propylene copolymer, a
tetrafluoroethylene/propylene/vinylidene fluoride copolymer, a
hexafluoropropylene/ethylene copolymer, a
tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer or a
vinylidene fluoride/tetrafluoroethylene/perfluoroalkyl vinyl ether
copolymer may, for example, be mentioned. One or more of them may
be used in combination. Among them, a tetrafluoroethylene/propylene
copolymer, a vinylidene
fluoride/tetrafluoroethylene/hexafluoropropylene copolymer or a
tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer is
preferably used from a reason that the chemical resistance is
excellent.
[0040] The fluorine content in the fluororubber is preferably at
least 40 mass %, more preferably at least 50 mass %, most
preferably at least 55 mass %. The fluororubber having a fluorine
content of at least 40 mass %, can give a crosslinked rubber
article excellent in the heat resistance, the chemical resistance,
the electrical insulating performance or the steam resistance.
[0041] As a preferred example of a fluororubber which is in the
market, "AFLAS150P" (tradename, manufactured by Asahi Glass
Company, Limited, a tetrafluoroethylene/propylene copolymer) may,
for example, be mentioned.
[Organic Peroxide]
[0042] The crosslinkable fluororubber composition of the present
invention may further contain an organic peroxide. Any organic
peroxide may be used so long as it can readily generate radicals,
under heating. Among them, it is preferred to use an organic
peroxide having a temperature at which the half-life period becomes
one minute, being from 130 to 220.degree. C. As specific examples,
1,1-di(t-hexylperoxy)-3,5,5-trimethylcyclohexane,
2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide,
t-butylcumyl peroxide, dicumyl peroxide,
.alpha.,.alpha.'-bis(t-butylperoxy)-p-diisopropylbenzene,
2,5-dimethyl-2,5-di(t-butylperoxy)-hexane,
2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, dibenzoyl peroxide,
t-butylperoxybenzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane,
t-butylperoxy maleic acid or t-hexylperoxyisopropyl monocarbonate
may, for example, be mentioned, and
.alpha.,.alpha.'-bis(t-butylperoxy)-p-diisopropylbenzene is
preferred. As the organic peroxide, one or more of them may be used
in combination.
[0043] The content of the organic peroxide is preferably from 0.1
to 5 parts by mass, more preferably from 0.2 to 4 parts by mass,
most preferably from 0.5 to 3 parts by mass, based on 100 parts by
mass of a fluororubber. When the content is within such a range,
the crosslinking efficiency of the organic peroxide becomes high,
whereby it is also possible to suppress the production amount by
invalid decomposition. However, in a case where the crosslinkable
fluororubber composition is subjected to crosslinking treatment by
irradiation with radioactive rays, it is not especially necessary
to incorporate the organic peroxide.
[Other Components]
[0044] In the crosslinkable fluororubber composition of the present
invention, a polyfunctional compound may further be incorporated as
a crosslinking coagent. The polyfunctional compound may, for
example, be triallyl cyanurate, triallyl isocyanurate, a triallyl
isocyanurate prepolymer, trimethallyl isocyanurate,
1,3,5-triacryloylhexahydro-1,3,5-triazine, triallyl trimellitate,
m-phenylenediaminebismaleimide, p-quinonedioxime, p,p'-dibenzoyl
quinonedioxime, dipropargyl terephthalate, diallyl phthalate,
N,N',N'',N'''-tetraallylterephthalamide or a vinyl group-containing
siloxane oligomer such as polymethylvinylsiloxane or
polymethylphenylvinylsiloxane. Among them, a polyallyl compound is
preferred, trially cyanurate, trially isocyanurate or trimethallyl
isocyanurate is more preferred, and triallyl isocyanurate is
further more preferred. By using the compound (A) and triallyl
isocyanurate in combination, it is possible to more effectively
suppress bleeding out from a crosslinked rubber article. As the
polyfunctional compound, one or more of them may be used in
combination. In a case where the polyfunctional compound is
incorporated, the content is preferably from 0.1 to 20 parts by
mass, more preferably from 0.2 to 10 parts by mass, based on 100
parts by mass of the compound (A). If the content of the
polyfunctional compound is less than 0.1 part by mass, the effect
of addition of the polyfunctional compound can hardly be obtained,
and if it exceeds 20 parts by mass, the moldability is likely to be
impaired.
[0045] The crosslinkable fluororubber composition of the present
invention may contain a filler. By incorporating the filler, it is
possible to improve the strength of a crosslinked rubber article
obtainable. As the filler, carbon black may preferably be used. Any
carbon black may be used so long as it is one used as blended with
a rubber. As specific examples, furnace black, acetylene black,
thermal black, channel black or graphite may be mentioned. Among
them, furnace black is more preferred, and as a specific example,
preferred is a grade such as HAF-LS, HAF, HAF-HS, FEF, GPF, APF,
SRF-LM, SRF-HM or MT, and most preferred is MT.
[0046] In a case where the filler is incorporated, the content is
preferably from 5 to 100 parts by mass, more preferably from 10 to
50 parts by mass, based on 100 parts by mass of a fluororubber. If
the content of the filler is less than 5 parts by mass, an effect
of addition of the filler can hardly be obtained, and if the
content exceeds 100 parts by mass, the elongation property of a
crosslinked rubber article is likely to deteriorate. When the
content of the filler is within the above range, the balance
between strength and elongation of a crosslinked rubber article
obtainable becomes good.
[0047] The crosslinkable fluororubber composition of the present
invention may contain other additives such as a reinforcing
material, a processing aid, a lubricant, a lubricant agent, a flame
retardant, an antistatic agent and a colorant.
[0048] The above reinforcing material may, for example, be a
fluororesin such as a polytetrafluoroethylene or an
ethylene/tetrafluoroethylene copolymer, glass fibers, carbon fibers
or white carbon. In the case of containing a reinforcing material,
the content is preferably from 5 to 200 parts by mass, more
preferably from 10 to 100 parts by mass, based on 100 parts by mass
of a fluororubber.
[0049] The above processing aid may, for example, be an alkali
metal salt of a higher fatty acid, and a stearate or a laurate is
preferred. In the case of containing a processing aid, the content
is preferably from 0.1 to 20 parts by mass, more preferably from
0.2 to 10 parts by mass, most preferably from 1 to 5 parts by mass,
based on 100 parts by mass of a fluororubber. If the amount of the
processing aid becomes too large, a bloom is likely to be formed on
the surface of a crosslinked rubber article, the hardness of a
crosslinked rubber article tends to be too high, or the chemical
resistance or the steam resistance is likely to be low. If the
amount of the processing aid is too small, the tensile strength of
the crosslinked rubber article tends to be remarkably low, or a
change in elongation or tensile strength after the heat aging
resistance tends to be remarkably large.
(Preparation Method of Crosslinkable Fluororubber Composition)
[0050] A preparation method of the crosslinkable fluororubber
composition of the present invention is not particularly limited,
and may be a known method. Preferred is a method of kneading a
fluororubber, the above compound (A) and, as the case requires, an
organic peroxide, a carbon black or other additives, by using a
kneading machine such as a twin roll, a Banbury mixer or a kneader.
Further, it is also possible to employ a preparation method in
which the above respective components are dissolved and dispersed
in a solvent, followed by kneading in such a state.
[0051] The order of mixing the above respective components is not
particularly limited, but it is preferred that, first of all,
components which are hardly reactive or decomposable by heat
generation is sufficiently kneaded with a fluororubber, and then
e.g. an organic peroxide as a component which is readily reactive
or decomposable, is blended therein, followed by kneading. At the
time of the kneading, it is preferred to cool the kneading machine
with water so as to keep a temperature within a range of from 80 to
120.degree. C. as a temperature at which crosslinking reaction does
not occur.
(Crosslinked Rubber Article)
[0052] The crosslinked rubber article of the present invention may
be obtainable by molding the crosslinkable fluororubber composition
of the present invention, by means of a known method such as
extrusion molding, injection molding, transfer molding or press
molding, followed by crosslinking. The molding and crosslinking may
be carried out at the same time, or they may respectively be
carried out separately in different steps.
[0053] For example, in the cavity of a mold having a shape for one
or a few crosslinked rubber articles, a crosslinkable fluororubber
composition containing an organic peroxide is filled, and the mold
is heated to obtain a crosslinked rubber article (primary
crosslinked product). The heating temperature is preferably from
130 to 220.degree. C., more preferably from 140 to 200.degree. C.,
most preferably from 150 to 180.degree. C. Further, as the case
requires, it is also preferred that this crosslinked rubber article
(primary crosslinked product) is further heated by e.g. an oven
employing electricity, heated air or steam as a heat source so as
to carry out crosslinking (hereinafter, also referred to as
secondary crosslinking), such being also preferred. By carrying out
the secondary crosslinking, a residue of an organic peroxide
contained in the crosslinked rubber article is decomposed and
volatilized to be reduced. A heating temperature during the
secondary crosslinking is preferably from 150 to 280.degree. C.,
more preferably from 180 to 260.degree. C., most preferably from
200 to 250.degree. C. A secondary crosslinking time is preferably
from 1 to 48 hours, more preferably from 4 to 24 hours.
[0054] Further, the crosslinkable fluororubber composition of the
present invention may also be crosslinked by applying ionizing
radiation such as electron beam or .gamma.-ray. To produce a
crosslinked rubber article by applying ionizing radiation, e.g. a
method of dissolving and dispersing the crosslinkable fluororubber
composition of the present invention in a proper solvent, applying
a resulting suspension solution to mold and then drying it, and
then applying ionizing radiation to obtain a crosslinked rubber
article, or a method of molding the crosslinkable fluororubber
composition of the present invention into a prescribed shape, and
then applying ionizing radiation to obtain a crosslinked rubber
article, may, for example, be mentioned. The exposure dose by
ionizing radiation may suitably be selected, but is preferably from
1 to 300 kGy, preferably from 10 to 200 kGy.
[0055] The crosslinked rubber article of the present invention can
suitably be used in a wide range as members such as a sealing
material such as an O ring, a sheet, a gasket, an oil seal or a
bearing seal, a diaphragm, a buffer material, a vibration absorber,
a wire covering material, an industrial belt, a tube/hose and a
sheet, in a wide field of e.g. a transportation machine such as an
automobile, a general instrument or an electrical apparatus. Among
them, it may suitably be used as a sealing material such as an O
ring, a sheet, a gasket, an oil seal or a bearing seal, from the
viewpoint of excellent flexibility at a low temperature, and
further from the viewpoint of excellent basic properties such as
strength, hardness, modulus or compression set.
EXAMPLES
[0056] Now, the present invention will be described in detail with
reference to Examples, but it should be understood that the present
invention is by no means restricted to such specific Examples.
[Materials to Be Used]
[0057] Blended components to be used in the following Examples and
Comparative Examples, are as follows.
(1) Fluororubber
[0058] Polymer 1: Tetrafluoroethylene/perfluoroalkyl vinyl ether
type bipolymer (trade name: AFLAS PFE1000, manufactured by Asahi
Glass Company, Limited, peroxide crosslinking type, fluorine
content: 72 mass %)
[0059] Polymer 2: Tetrafluoroethylene/propylene/vinylidene fluorine
terpolymer (trade name: AFLAS 200P, manufactured by Asahi Glass
Company, Limited, peroxide crosslinking type, fluorine content: 60
mass %)
[0060] Polymer 3: Tetrafluoroethylene/propylene bipolymer (trade
name: AFLAS 100S, manufactured by Asahi Glass Company, Limited,
peroxide crosslinking type, fluorine content: 57 mass %)
(2) Crosslinking Coagent
[0061] Crosslinking coagent 1: A composition having, as a main
component, a compound (A2') obtained in the following Preparation
Example, and having Mn of 2,900 and Mw/Mn of 1.14
[0062] TAIC: Triallyl isocyanurate (manufactured by Nippon Kasei
Chemical Co., Ltd.)
(3) Organic Peroxide
[0063] Perbutyl P:
.alpha.,.alpha.'-Bis(t-butylperoxy)-p-diisopropylbenzene (trade
name: PERKADOX 14, manufactured by NOF CORPORATION)
[0064] PERHEXA 25B: 3,5-Dimethyl-2,5-di-t-butylperoxyhexane (trade
name: PERHEXA 25B, manufactured by NOF CORPORATION)
(4) Filler
[0065] MT Carbon: Carbon black (grade: MT Carbon, manufactured by
CANCARB)
(5) Processing Aid
[0066] NONSOUL SN-1: Sodium stearate (manufactured by NOF
CORPORATION)
(Preparation of Crosslinking Coagent 1)
[0067] The interior of a 100 mL round flask having a stirrer chip
put therein, was sufficiently replaced with nitrogen. 20.0 g of a
composition having the following compound (A0-1) as a main
component and 20 g of dichloropentafluoropropane were charged in
the round flask, followed by intense stirring. After one hour, a
mixture of 1.5 g of CH.sub.2.dbd.CHCH.sub.2NH.sub.2 and 20 g of
dichloropentafluoropropane was slowly dropwise added over a period
of 0.5 hour from a dropping funnel provided on the upper part of
the round flask. After completion of the dropwise addition, the
interior was heated to 50.degree. C., stirred continuously for 6
hours, and then cooled to room temperature.
##STR00009##
[0068] A crude fluid obtained was concentrated by an evaporator,
and a residue was washed twice with 0.1 L of n-hexane to obtain
18.8 g of a composition as a colorless liquid at room temperature.
This composition was such that at least 99.9 mol % of
"--C(O)OCH.sub.2CH.sub.3" of the above compound (A0-1) was
converted to "--C(O)NHCH.sub.2CH.dbd.CH.sub.2", and the following
compound (A2') was a main component. Further, an average value of
b1+b2+b3 in the composition having the formula (A2') as a main
component was 21.1 as a result of an NMR measurement. This
composition was regarded as a crosslinking coagent 1.
##STR00010##
[0069] The compound (A2') was subjected to NMR analysis, HPLC
analysis and GPC analysis under temperature conditions of room
temperature (25.degree. C.), whereby formation of the compound
(A2') was confirmed.
<NMR Analysis>
[0070] As a standard substance of .sup.1H-NMR (300.4 MHz),
tetramethylsilane was used. Further, as a standard substance of
.sup.19F-NMR (282.7 MHz), CFCl.sub.3 was used. Further, as a
solvent, CCl.sub.2FCClF.sub.2 was used unless otherwise
specified.
<HPLC Analysis>
[0071] The compositional ratio of the compounds in the composition
was measured by a HPLC analyzer (Prominence, manufactured by
Shimadzu Corporation) under the following conditions. Specifically,
in each run, the HFIP concentration in the mobile phase was
gradually increased from 0% to 100%, and the mass ratio of
compounds in the composition eluted, was analyzed.
[0072] Analytical column: Normal phase silica gel column (SIL-gel,
manufactured by YMC Co., Ltd.)
[0073] Mobile phase: Dichloropentafluoropropane (ASAHIKLIN AK-225G,
manufactured by Asahi Glass Company, Limited) and HFIP
[0074] Mobile phase flow rate: 1.0 mL/min
[0075] Column temperature: 37.degree. C.
[0076] Detector: Evaporative light scattering detector
<GPC Analysis>
[0077] A number average molecular weight (Mn) and a mass average
molecular weight (Mw) were measured by GPC in accordance with
JP-A-2001-208736 under the following conditions, and Mw/Mn was
determined.
[0078] Mobile phase: Solvent mixture of dichloropentafluoropropane
(ASAHIKLIN AK-225SEC grade 1, manufactured by Asahi Glass Company,
Limited) and hexafluoroisopropyl alcohol
(dichloropentafluoropropane/hexafluoroisopropyl alcohol=99/1 in
volume ratio)
[0079] Analytical column: Serially connected two PLgel MIXED-E
columns (manufactured by Polymer Laboratories)
[0080] Molecular weight standard samples: Four perfluoropolyethers
having Mw/Mn less than 1.1 and molecular weights of from 2,000 to
10,000 and one perfluoropolyether having Mw/Mn of at least 1.1 and
a molecular weight of 1,300
[0081] Mobile phase flow rate: 1.0 mL/min
[0082] Column temperature: 37.degree. C.
[0083] Detector: Evaporative light scattering detector
[0084] As a result of the HPLC analysis, the crosslinking coagent 1
obtained was found to be a composition containing 7.0 mass % of a
monofunctional compound, 30.8 mass % of a bifunctional compound,
42.9 mass % of a trifunctional compound (A2'), 18.1 mass % of a
tetrafunctional compound and 1.2 mass % of a compound having more
than 4 functional groups. Accordingly, the proportion of the
compound (A) having 3 or more functional groups, which is effective
for three dimensional crosslinking, was 62.2 mass %. A
monofunctional compound and a bifunctional compound were compounds
having a small number of functional groups, which were formed as
by-products in a fluorination step, and even though such compounds
are not the compound (A), the crosslinking coagent 1 was used as it
is without separating the compounds.
[0085] As a result of the GPC analysis, a number average molecular
weight (Mn) of the crosslinking coagent 1 was 2,900, and Mw/Mn was
1.14. Further, it was confirmed that the crosslinking coagent 1 has
no structure of --OCF.sub.2O--.
[0086] As a result of the NMR analysis, the following results were
obtained as .sup.1H-NMR spectrum and .sup.19F-NMR spectrum.
[0087] .sup.1H-NMR spectrum .sigma. (ppm): 7.09, 5.92, 5.38 to
5.20, 3.72
[0088] .sup.19F-NMR spectrum .sigma. (ppm): -54.0, -77.6, -88.2 to
-92.0, -135.0 to -139.0
[Measurement of Crosslinked Rubber Article]
[0089] TR-10 value, hardness (HS), tensile strength (T.sub.B),
elongation (E.sub.B), compression set and 100% tensile stress
(M.sub.100) of a crosslinked rubber article in each of the
following Examples and Comparative Examples, were measured by the
following methods.
[0090] Low-temperature elastic retraction test: In accordance with
JIS K6261, the low temperature elastic retraction test was carried
out by a low temperature elastic retraction tester (TR Tester,
manufactured by Ueshima Seisakusho Co., Ltd.) to measure the TR-10
value.
[0091] Hardness: In accordance with JIS K6253, hardness (HS) was
measured by a durometer type A hardness test at 23.degree. C. When
the hardness is from 60 to 90, the article is suitable as a sealing
material.
[0092] Tensile strength: In accordance with JIS K6251, tensile
strength (T.sub.B) was measured at 23.degree. C. When the tensile
strength (T.sub.B) is at least 10 MPa, the article is suitable as a
sealing material.
[0093] Elongation: In accordance with JIS K6251, elongation
(E.sub.B) was measured at 23.degree. C. When the elongation
(E.sub.B) is at least 160%, the article is suitable as a sealing
material.
[0094] Compression set: In accordance with JIS K6262, compression
set was measured at 200.degree. C. for 70 hours.
[0095] 100% tensile stress (modulus): In accordance with JIS K6251,
100% tensile stress (M.sub.100) was measured at 23.degree. C. When
the 100% tensile stress (M.sub.100) is from 2 to 17 MPa, the
article is suitable as a sealing material.
Example 1
[0096] 100 Parts by mass of the polymer 1, 1 part by mass of the
PERHEXA 25B, 5 parts by mass of the crosslinking coagent 1, 20
parts by mass of the MT-Carbon and 1 part by mass of NONSOUL SN-1
were kneaded by a twin screw roller to obtain a peroxide
crosslinkable fluororubber composition. The composition was formed
into a sheet with 100 mm.times.100 mm.times.2 mm by hot pressing at
170.degree. C. (primary crosslinking). Further, this sheet was put
in a gear oven for 4 hours at 250.degree. C., to carry out
secondary crosslinking.
[0097] From a crosslinked rubber sheet obtained, four sheets of
samples were punched out by a #3 dumbbell to measure the properties
of the crosslinked rubber. Further, in accordance with JIS K6250,
four samples for low-temperature elastic retraction test were
prepared to carry out a low-temperature elastic retraction test.
The results are shown in Table 1. This crosslinked rubber article
has a hardness (HS) of 61, a tensile strength (T.sub.B) of 19.8
MPa, an elongation (E.sub.B) of 232%, a 100% tensile stress
(M.sub.100) of 9.0 MPa, a compression set of 30% and a TR-10 value
of -7.6.degree. C.
Examples 2 to 6 and Comparative Examples 1 to 3
[0098] A crosslinked rubber sheet was prepared in the same manner
as in Example 1 except that the respective blend components were
changed as shown in Table 1, and the properties of the crosslinked
rubber article were measured in the same manner as the above.
TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1
Ex. 4 Ex. 2 Ex. 5 Ex. 6 Ex. 3 Blend Fluororubber Polymer 1 100 100
100 100 composition Polymer 2 100 100 (part by mass) Polymer 3 100
100 100 Crosslinking Crosslinking 5 10 25 25 10 25 coagent coagent
1 TAIC 5 5 5 Organic Perbutyl P 1 1 1 1 1 peroxide PERHEXA 25B 1 1
1 1 Filler MT Carbon 20 20 20 20 20 20 20 20 20 Processing aid
NONSOUL SN-1 1 1 1 1 1 1 1 1 1 Ordinary state Tensile strength
(T.sub.B) [MPa] 19.8 19.2 11.2 17.9 9.4 17.0 15.3 11.6 18.0
physical 100% Tensile stress (M.sub.100) [MPa] 9.0 8.7 7.2 7.0 2.3
5.0 2.0 2.5 7.0 properties Elongation (E.sub.B) [%] 232 231 203 190
326 270 516 362 240 Hardness (HS) 61 60 60 73 61 69 59 63 70
Specific gravity (SG) [g/cm.sup.3] 2.00 1.98 1.97 2.00 1.68 1.61
1.59 1.61 1.59 Compression set [%] 30 36 42 26 48 36 39 50 36
Low-temperature Low-temperature elastic retraction -7.6 -9.7 -11.9
-1.0 -12.0 -7.0 0.5 -1.7 3.6 characteristics test TR 10 value
[0099] As shown in Table 1, the crosslinked rubber articles in
Examples 1 to 6 have the same ordinary state physical properties as
the crosslinked rubber articles in Comparative Examples 1 to 3, a
low TR-10 value, and an excellent flexibility at a low temperature.
Further, as the amount of the crosslinking coagent 1 added is
increased, the TR-10 value was lowered, and the flexibility at a
low temperature improved.
[0100] On the other hand, the crosslinked rubber articles in
Comparative Examples 1 to 3, which were obtained by crosslinking a
fluororubber composition containing no crosslinking coagent 1
(compound (A2)) were such that the TR-10 value of each crosslinked
rubber article obtained by using the same fluororubber was high,
and the flexibility at a low temperature was poor, as compared with
Examples 1 to 6.
INDUSTRIAL APPLICABILITY
[0101] The crosslinked rubber article of the present invention can
suitably be used in a wide range as members such as a sealing
material such as an O ring, a sheet, a gasket, an oil seal or a
bearing seal, a diaphragm, a buffer material, a vibration absorber,
a wire covering material, an industrial belt, a tube/hose and a
sheet in a wide field of e.g. transportation machine such as an
automobile, a general instrument or an electrical apparatus.
[0102] This application is a continuation of PCT Application No.
PCT/JP2010/067161 filed on Sep. 30, 2010, which is based upon and
claims the benefit of priority from Japanese Patent Application No.
2009-229424 filed on Oct. 1, 2009. The contents of those
applications are incorporated herein by reference in its
entirety.
* * * * *